Magnetic video pilot signal recording/reproducing system

Abstract

In a video tape recorder of the rotary two-head helically scanning type, a magnetic recording/reproducing system provided with a mode judging device in which a video signal is recorded onto a recording track in a multiplex manner together with a pilot signal for use in judgement of the recording time mode and when the record is reproduced the pilot signal is detected to thereby judge the recording time mode.

We claim: 
     
       1. A magnetic recording system comprising: video signal processing means including a separating circuit for separating at least one of a luminance signal and a chrominance signal from a video signal, a frequency-modulating circuit for receiving said luminance signal and for frequency-modulating said received luminance signal, frequency converting means for receiving said chrominance signal and for converting a frequency of said received chrominance signal into a low-frequency band, and mixing circuit means for mixing said frequency-modulated luminance signal and said low-frequencyconverted chrominance signal so as to provide a video signal for recording;   recording means for recording said video signal from said video signal processing means onto a magnetic tape, said recording means including at least a first and second rotary magnetic head for forming recording tracks for at least a first and a second channel in an oblique direction on said magnetic tape and for recording field video signals of said first and second channels onto said first and second channel recording tracks:   pilot signal generating means for generating a pilot signal;   means for adding said pilot signal from said pilot signal generating means to said video signal from said video signal processing means to be multiplexed with said video signal;   said video signal processing means further including reference signal generating means for generating a reference signal having a frequency which is an integer multiple of a chrominance subcarrier of said low-frequencyconverted chrominance signal; and   said pilot signal generating means being coupled with said reference signal generating means and including frequency dividing means for frequency-dividing said reference signal from said reference signal generating means to produce a low-frequency pilot signal.   
     
     
       2. A magnetic recording system according to claim 1, wherein said reference signal generating means is connected with said frequency converting means for supplying said reference signal to said frequency converting means. 
     
     
       3. A magnetic recording system according to claim 2, wherein said reference signal has a frequency which is eight times the frequency of said chrominance subcarrier of said low-frequency converted chrominance signal. 
     
     
       4. A magnetic recording system according to claim 2, wherein said reference signal generating means further includes a reference signal generating circuit for generating a signal having a frequency based on a horizontal synchronizing frequency of said video signal as said reference signal, a frequency dividing circuit for receiving an output of said reference signal generating circuit and for frequency-dividing said output signal into a predetermined low-frequency signal, and phase-shifting circuit for receiving said predetermined low-frequency signal from said frequency dividing circuit and for phase-shifting said predetermined low-frequency signal by 90 degrees or 180 degrees every horizontal period; said frequency converting means of said video signal processing means further includes a frequency converting circuit for receiving said chrominance signal from said separating circuit and an output of said phase-shifting circuit and for causing the frequency of said chrominance signal to be equal to the frequency of said predetermined low-frequency signal produced by said frequency-dividing circuit; and   said frequency dividing means of said pilot signal generating means includes a frequency dividing circuit for receiving said reference signal and for frequency-dividing said received reference signal, and deriving means for deriving said pilot signal from said frequency dividing circuit and for supplying said pilot signal to said video signal processing means.   
     
     
       5. A magnetic recording system according to claim 4, wherein said reference signal generating circuit includes a phase locked loop circuit for producing a frequency which is N (N being integer) multiple of said horizontal synchronizing frequency of said video signal f H , said frequency dividing circuit of said pilot signal generating means receiving an output signal of said phase locked loop circuit and for producing a four-frequency pilot signal having four low-frequencies (f 1 , f 2 , f 3 , f 4 ), said pilot signal deriving means includes frequency selecting means for receiving said four frequency pilot signal and for cyclically selecting said four low-frequencies. 
     
     
       6. A magnetic recording system according to claim 5, characterized in that said frequency dividing circuit of said pilot signal generating means includes at least four frequency dividers for frequency-dividing said output frequency of said phase locked loop circuit so as to produce said four-frequency pilot signal having four frequencies (f 1 , f 2 , f 3 , f 4 ) each having an offset of a value within a range from 0.2f H  to 0.7f H  with a relation f 1  -f 2  =f 3  -f 4  thereamong. 
     
     
       7. A magnetic recording system according to claim 4, wherein said reference signal generating circuit includes a phase locked loop circuit for producing a frequency which is 3N (N being integer) multiple of said horizontal synchronizing frequency of said video signal f H , said frequency dividing circuit of said reference signal generating means including a one-eighth frequency dividing circuit for receiving an output signal of said phase locked loop circuit and for frequency-dividing said received output signal of said phase locked loop circuit into substantially one-eighth, said frequency dividing circuit of said pilot signal generating means receiving an output of said phase locked loop circuit for producing a four-frequency pilot signal having four low-frequencies (f 1 , f 2 , f 3 , f 4 ) said pilot signal deriving means includes frequency selecting means for receiving said four-frequncy pilot signal and for cyclically selecting said four low-frequencies. 
     
     
       8. A magnetic recording system according to claim 2, wherein said reference signal generating means of said video signal processing means includes a phase locked loop circuit for producing a frequency which is 3N (N being integer) multiple of a horizontal synchronizing freuqency of said video signal, a one-eighth frequency-dividing circuit for frequency-dividing an output frequency of said phase locked loop circuit into a one-eighth frequency-divided signal, a phase-shifting circuit for receiving said one-eighth frequency-divided signal for phase-shifting said received one-eighth frequency-divided signal by 90 degrees or 180 degrees only one side field every horizontal period, an oscillating circuit for oscillating with the same frequency as that of a chrominance subcarrier of said chrominance signal of said video signal, and a first frequency converter for mixing the respective outputs of said phase-shifting circuit and said oscillating circuit to provide a local oscillating signal, said frequency converting means of said video signal processing means includes a second frequency converter for mixing said local oscillating signal and said chrominance signal to cause the frequency of said chrominance signal to be equal to the frequency of said one-eighth frequency-divided signal so as to obtain said low-frequency converted chrominance signal, and means for leading said low-frequency converted chrominance signal to said first and second rotary magnetic heads, and said frequency dividing means of said pilot signal generating means frequency-dividing an output frequency of said phase locked loop circuit to produce a four-frequency pilot signal having four signals (f 1 , f 2 , f 3 , f 4 ), and a frequency selecting circuit for cyclically selecting said four-frequency pilot signal. 
     
     
       9. A magnetic recording system according to claim 2, wherein said reference signal generating means of said video signal processing means includes first carrier generating means for generating a first carrier having a frequency which is N (N being an integer) multiple of a horizontal synchronizing frequency of said video signal, first frequency dividing means for frequency-dividing said first carrier frequency into substantially one-eighth, first frequency converting means for receiving an output signal of said first frequency dividing means and a second carrier having a frequency which is substantially the same as that of a carrier chrominance signal in said input video signal to thereby produce a frequency which is a sum of the frequencies of the received signals, and said frequency converting means of said video signal processing means receiving a carrier chrominance signal extracted from said video signal and an output signal of said first frequency converting means to thereby produce a difference frequency between the receiving signals, and said frequency driving means of said pilot signal generating means including first dividing means for frequency-dividing said first carrier frequency into substantially one-half, second dividing means for frequency-dividing an output of said first dividing means into at least four frequencies, and frequency selecting circuit means for selecting outputs of said second dividing means. 
     
     
       10. A magnetic recording system according to claim 1, further comprising recording-time mode changing-over means for controlling a feeding speed of said magnetic tape so as to change over a recording time mode for recording operation onto said magnetic tape between at least a first and a second recording time modes, said pilot signal generating means including means for generating a first pilot signal corresponding to said first recording time mode and a second pilot signal corresponding to said second recording time mode and for alternatively producing one of said first and second pilot signals in accordance with the selection of one of said first and second recording time modes. 
     
     
       11. A magnetic recording system according to claim 10, wherein said pilot signal generating means generates said first and second pilot signals such that when said first and second pilot signals are recorded in said recording means the respective recording arrangements thereof are mirror symmetric.